The present invention relates to machines for the making of cigarettes, cigars, cigarillos, filter rods or analogous rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in the construction of those parts of such machines wherein a shower of tobacco particles or the like is converted into a continuous stream. For the sake of simplicity, the invention will be described with reference to machines which are used for the production of cigarettes, it being understood, however, that the invention can be embodied with equal advantage in other types of machines wherein particulate material is showered into a channel to form a growing stream which is thereupon draped into a web of wrapping material to form a continuous rod.
A cigarette making machine comprises a so-called distributor which showers particles of shredded tobacco into an elongated channel wherein the particles are intercepted and entrained by one side of a foraminous belt the other side of which is adjacent to a suction chamber. The intercepted particles form a growing tobacco stream which is thereupon converted into a rod-like filler of constant cross-section, draped into a web of cigarette paper and subdivided into discrete cigarettes of desired length. As a rule, the suction chamber forms part of or includes or is adjacent to the elongated channel which has two parallel side walls and an air-permeable bottom wall between the side walls. The bottom wall is disposed between the belt and the suction chamber and enables air to flow through the pores or interstices of the moving belt and into the suction chamber so that the particles of tobacco which are showered to the one side of the belt adhere thereto regardless of whether the growing stream is formed at the upper side or at the underside of the belt. The bottom wall normally consists of ceramic bars which extend at right angles to the direction of movement of the belt. When the machine is in use, the currents of air which traverse the belt and the bottom wall on their way into the suction chamber generate noise which consists of whistling sounds and is highly unpleasant to the attendants. It is believed that the cause for generation of such noise is to be found in the orientation of bars which form the bottom wall of the channel, and in the orientation of filaments of which the belt consists. The majority of filaments extend at right angles to the direction of movement of the belt, i.e., they are parallel or nearly parallel to the bars of the bottom wall.